Variable speed pyrolytic waste treatment system

ABSTRACT

The inventive subject matter is directed toward a pyrolytic waste treatment system comprising a pyrolysis chamber and a movement mechanism adapted to move waste through the pyrolysis chamber at different speeds along the length of the pyrolysis chamber.

This application claims the benefit of U.S. provisional application No.60/497397 filed on 21 Aug. 2003 incorporated herein by reference in itsentirety.

FIELD OF THE INVENTION

The field of the invention is pyrolytic waste treatment.

BACKGROUND OF THE INVENTION

Pyrolysis is a known method for treatment of waste. Examples ofpyrolytic waste treatment systems can be found in U.S. Pat. Nos.4,759,300, 5,653,183, 5,868,085, and 6,619,214. Unlike incineration,pyrolysis is the destructive decomposition of waste materials usingindirect heat in the absence of oxygen. Burning wastes throughincineration with direct flame in the presence of oxygen can beexplosive, causing turbulence in the burning chamber, which fosters arecombination of released gases. Waste destruction in an oxygen-richatmosphere makes conversion far less complete, is highly inefficient andcreates harmful substances.

In contrast, the pyrolytic process employs high temperature in, mostdesirably, an atmosphere substantially free of oxygen (for example, in apractical vacuum), to convert the solid components of waste to a mixtureof solids, liquids, and gases with proportions determined by operatingtemperature, pressure, oxygen content, and other conditions. The solidresidue remaining after pyrolysis commonly is referred to as char. Thevaporized product of pyrolysis is often further treated by a processpromoting oxidation, which “cleans” the vapors to eliminate oils andother particulate matter there from, allowing the resultant gases thento be safely released to the atmosphere.

What has long been needed and heretofore has been unavailable is animproved pyrolytic waste treatment system that is highly efficient, iseasy to maintain, is safe, reliable and capable of operation with a widevariety of compositions of waste materials, and that can be constructedand installed at relatively low cost. The thrust of the presentinvention is to provide such an improved pyrolytic waste treatmentsystem.

SUMMARY OF THE INVENTION

The present subject matter is directed toward a pyrolytic wastetreatment system in which a movement mechanism is used to move wastethrough the pyrolysis chamber at various rates along the length of thepyrolysis chamber.

In another aspect, a method of pyrolyzing waste in an elongated chambercomprises moving the waste through the chamber at different rates alongthe length of the chamber.

Various objects, features, aspects and advantages of the presentinvention will become more apparent from the following detaileddescription of preferred embodiments of the invention, along with theaccompanying drawings in which like numerals represent like components.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a schematic of a pyrolytic waste treatment system.

DETAILED DESCRIPTION

In FIG. 1, a pyrolytic waste treatment system 100 generally comprises apyrolytic chamber 910 and a waste movement mechanism 960.

It is contemplated that it would be beneficial to vary the rate ofmovement of material through a pyrolysis chamber. In particular,material might move at a slower rate when it first enters the chamberand move at a faster rate after it has been heated and as is movedtoward the chamber exit. It is contemplated that the use of paddles or ascrew in which the pitch of the paddles or the screw threads varies fromone end of the chamber to the other would prove beneficial. It should berecognized that other methods and devices may be used to move materialthrough the chamber including, for example, using gravity, magnetism,and forced air. With regard to using magnetism, it is furthercontemplated that a product could be statically charged within amagnetic field. Other methods and devices are also contemplated so longas they move the product through the chamber and are in accordance withthe inventive concepts described herein.

It is preferred that the speed at which waste moves through the chamber910, and the temperature of the chamber 910 will both vary along thelength of the chamber 910. At least in part in order to minimize heatloss, the ends of the chamber are generally cooler than portions of thechamber closer to the center of the chamber. As such, waste movementmechanism 960 varies along the length of pyrolysis chamber 910 toincrease movement speed at the cooler ends, and to slow it down in theactive heating region.

In section 911 of chamber 910, mechanism 960 comprises screw conveyorsection 961 adapted to move waste quickly through section 911 away fromwaste inlet 930. In section 912, where active heating occurs, mechanism960 comprises a first paddle section 962 wherein the paddles areoriented primarily to agitate, mix, and expose waste to heat rather thanmove it along the chamber 910. Movement of waste through section 912occurs to a large extent from being pushed by waste moving into section912 from section 911. In section 913, a second paddle section 963 haspaddles oriented to move waste along section 913 to char outlet 940. Thescrew conveyer and paddles are coupled to, and may be integrally formedwith, a drive shaft 969.

Screw conveyor section 961 of mechanism 960 is in some embodiments about5 feet long, and the screw blades are pitched at varying degrees. Insome embodiments, section 962 is about 20 feet long, and comprisesapproximately 42 paddles, wherein at least some of the paddles areoriented such that at least one side is substantially parallel to thecenter axis of shaft 969. In contrast, the section 963 of mechanism 960(in some embodiments the last 5 feet of mechanism 960) of paddles systemare pitched/angled to move the waste that has already reached the propertemperature quickly out of the actively heated zone.

Although a movement mechanism comprising a screw and paddles mounted toa single drive shaft is shown, alternative embodiments may usealternative apparatus and or methods to vary the speed at which materialmoves through pyrolysis chambers. As an example, some embodiments mayutilize multiple movement mechanisms rather than a single movementmechanism. Others may utilize paddles along the entire length of thechamber, may utilize paddles followed by a screw conveyor, may utilizeonly a screw conveyer or may utilize an entirely different type ofmechanism such as one or more flat conveyers.

A pyrolytic waste treatment system, particularly a continuous feedsystem adapted to move waste being treated at different speeds along thelength of a pyrolysis chamber. Variances in speed my result from varyingthe pitch of paddles and/or screws used to move the waste along thelength of the pyrolysis chamber.

Energy savings and improved treatment can be achieved in a pyrolysistreatment system which varies the rate of movement of material through apyrolysis chamber. In particular, material moving material at a slowerrate when towards the center of the chamber relative to when it firstenters the chamber and when it approaches the chamber exit minimizesheat losses at the chamber entrance and exit while insuring the waste isadequately heated for treatment. Varying the rate of movement may beachieved through the use of paddles or a screw in which the pitch of thepaddles or the screw threads varies from one end of the chamber to theother.

Thus, specific embodiments and applications of a pyrolytic system havebeen disclosed. It should be apparent, however, to those skilled in theart that many more modifications besides those already described arepossible without departing from the inventive concepts herein. Theinventive subject matter, therefore, is not to be restricted except inthe spirit of the appended claims. Moreover, in interpreting both thespecification and the claims, all terms should be interpreted in thebroadest possible manner consistent with the context. In particular, theterms “comprises” and “comprising” should be interpreted as referring toelements, components, or steps in a non-exclusive manner, indicatingthat the referenced elements, components, or steps may be present, orutilized, or combined with other elements, components, or steps that arenot expressly referenced.

1. A pyrolytic waste treatment system, comprising: a pyrolysis chamber;and a movement mechanism adapted to move waste through the pyrolysischamber at different speeds along the length of the pyrolysis chamber.2. The system of claim 1, wherein the movement mechanism comprises ascrew.
 3. The system of claim 1, wherein the movement mechanismcomprises brushes.
 4. The system of claim 1, wherein the movementmechanism comprises a set of paddles having pitches that vary along atleast a portion of the length of the pyrolysis chamber.
 5. The system ofclaim 1, wherein the movement mechanism comprises a screw conveyor and aplurality of paddles wherein the paddles vary in pitch along at least aportion of the length of the pyrolysis chamber.
 6. The system of claim5, wherein the screw conveyer and plurality of paddles are all coupledto a common shaft that extends along the length of the pyrolysischamber.
 7. The system of claim 1, wherein the movement mechanism isadapted to move waste through the pyrolysis chamber at a faster rateneat the ends of the chamber relative to the center of the center of thechamber.
 8. A method of pyrolyzing waste in an elongated chambercomprising moving waste through the chamber at different rates along thelength of the chamber.
 9. The method of claim 8, wherein paddles havingvaried pitches are used to move waste through the chamber.
 10. Themethod of claim 8, wherein a screw conveyer is used to move waste at anend of the chamber at which it enters the chamber, and a plurality ofpaddles are used to move the waste through the remainder of the chamber.